OK, I just did a (somewhat) controlled test by playing a 295.8 HZ test tone from my computer speakers at a consistent volume and set the gain in canon audio menu to 25% The recorded MLV and .H264 clips were within 1db of each other. This is perfectly acceptable. Perhaps that night at the concert I lost my gain settings after a battery pull or something stupid. I have a healthy suspicion that the difference becomes more pronounced at lower gain settings, or.... the .h264 encoder features an audio limiter that was active at concert volumes, but transparent in my test. It's too late for me to scream at my camera tonight, but I will test again tomorrow with varying signal strength and see if I can get to the bottom of this.
